Laterally disposed coterminously adjacent multicolor area containing graphic reproduction receptor and electrophotographic process of using same



Och 1965 c. s. MILLER ETAL 3,212,337

LATERALLY DISPOSED COTERMINOUSLY ADJACENT MULTICOLOR AREA CONTAINING GRAPHIC REPRODUCTION RECEPTOR AND ELECTROPHOTOGRAPHIC PROCESS OF USING SAME Filed April 7. 1961 HQ. 2 F1 3 HH um Cr Yb M Cr (1 mil .1 Cr

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//v1//vr025 CAPLSM/LLBQ BmaNIIZ/VEHER United States Patent LATERALLY DISPOSED COTERMINOUSLY AD- JACENT MULTICOLOR AREA CONTAINING GRAPHIC REPRODUCTION RECEPTOR AND ELECTROPHOTOGRAPHIC PROCESS OF USING SAME Carl S. Miller, St. Paul, Minn., and Byron W. Neher, Hudson, Wis., assignors to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware Filed Apr. 7, 1961, Ser. No. 101,529 11 Claims. (Cl. 96-1) This invention relates to a reproduction process. In another aspect this invention relates to a novel graphic reproduction receptor. In still another aspect this invention relates to a process and a copy sheet for the reproduction in color of colored images and patterns.

Basically, there are two types of color reproduction processes; the additive color process and the subtractive color process. The Findlay process and the Dufay process are examples of additive color processes. In the Findlay process a very fine mosaic (checkerboard) filter consisting of red, green, and blue elements (the three basic colors necessary for color reproduction) is printed on a glass plate. This is placed in direct contact with a panchromatic silver halide emulsion layer on glass. The color picture is exposed through the mosaic filter onto the silver halide layer. The filter is then taken away and the photographic plate processed by reversal technique to yield a positive image. When the finished plate is held in register with the mosaic filter and viewed by transmitted white light, a color picture is observed. The operation of the system is briefly as follows: In a red area of the picture, light will pass only through the red elements of the mosaic and the film will be exposed only in these areas. On developing by reversal technique, these areas become clear and the unexposed areas behind the green and blue elements become black. Thus, when the filters are put back in place, the red elements are over clear spots and the blue and green elements over black spots and only red light can be seen on viewing through in this area. The intensity of the red light making the exposure of the silver halide layer controls the degree to which it will develop (by reversal) to a clear area. Thus, the tone of the red is controlled and properly reproduced. Similar reasoning holds for the green and blue filters. Since all the filter elements are extremely small, the picture viewed by transmitted light looks like a full color picture in hue and tone.

The Dufay process is essentially the same as the Findlay process except that the color mosaic is printed with colored lacquers on film stock and the silver halide emulsion is coated directly on the colored film. This solves the problem of registering the filter with the developed image for viewing.

These two processes are suitable only for viewing by transmitted light of high intensity, since in an area of a given color, two-thirds of that area must be blacked out to hide the unwanted colors. These processes are not useful with opaque (paper) stock where the reproduction must be viewed by reflected light.

The most successful of the photographic color processes have been those based on the subtractive tri-pack. The tri-pack consists of three layers coated one on top of the next, one layer being called the magenta layer, another called the cyan layer, and the third being called the yellow layer. Each subtractive color transmits twothirds of the spectrum and absorbs one-third. The combination of cyan, magenta, and yellow layers appears black. The combination of magenta and yellow layers appears red, magenta and cyan appear blue, and yellow and cyan appear green. In one method of subtractive color photography, red light causes the destruction of the cyan dye but has no effect on the dyes of the other two layers. When red light falls on the subtractive tripack, the cyan is removed and a red color results. By exactly the same process green light destroys the magenta dye and leaves a green color (the cyan and yellow layers viewed subtractively). Similarly, blue light destroys the yellow layer and blue is produced.

The above technique is used in the Gaspar (or dye bleach) process of color photography. In this process, the cyan colored layer contains in it a silver halide emulsion which is selectively sensitive to red light and a cyan colored dye. The magenta layer contains in it a silver halide emulsion which is sensitive only to green light and a magenta colored dye, and the yellow layer is sensitive only to blue light and contains a yellow dye. The three layers, one over the other, look essentially black. When a positive color picture is projected on this black sheet, the red portions affect the silver halide emulsion in the cyan layer only; the green portions the magenta layer; and the blue portions the yellow layer. The exposed tri-pack is next developed and fixed as an ordinary silver halide type of sheet. In the cyan layer, silver metal is produced in proportion to the red image; in the magenta layer silver is produced in proportion to the green image; and in the yellow layer, in proportion to the blue image.

The sheet is next placed in an acid thiourea solution containing a catalyst. In this solution the silver metal causes the reduction of (bleaching of) the dyes in proportion to the amount of silver metal present in each layer. Lastly, the silver salts and any remaining free silver are dissolved out; the print washed and dried. The result is a full-colored, positive picture produced by the subtractive eflect of light going through the three layers and reflecting back off the white paper on which they are coated.

All modern color processes are variations of the sub tractive tri-pack. In the well known Ektachrome positive film, the dyes are formed chemically rather than by being bleached away or destroyed. In the three layers are essentially the three silver halide emulsions selectively sensitive each to one of blue, green, or red light. There is also present in the blue sensitive layer a relatively colorless chemical which will later produce a yellow color. Similar arrangements are made in each of the other layers to produce in later development magenta and cyan. The first development step utilizes silver developer which uses up silver halide in the exposed areas in each layer (converts it to silver) in proportion to the blue, green, and red exposures, respectively. After the first development step, unused silver halide is now present in proportion to the positive image of each color. The film is then flooded with white light to expose all the remaining silver halide, and this is then developed with a special developer which as it forms silver metal from silver halide changes to a compound which in turn reacts with the other special chemicals in each layer to produce yellow, magenta, and cyan, respectively, in proportion to the positive images. The silver metal present is next chemically removed and the film washed and dried.

The present process and reproduction receptor overcomes the disadvantages of the above techniques for color reproduction in that the present invention is not limited to type of receptor, is unusually simple, and requires only a simple development stage. In essence, the present invention is a combination of the subtractive color technique with photoconductive materials as the radiation responsive element rather than silver halide type materials.

An object of this invention is to provide a new reproduction process.

Another object of this invention is to provide a new and useful reproduction receptor or copy sheet.

Still another object is to provide a simple development technique for developing a reproduction in color.

Yet another object is to provide new color responsive combinations of materials.

A further object of this invention is to provide a subtractive color process having superior color rendition and contrast as compared to an additive color process.

Another object is to provide new methods for preparing light responsive receptors.

Another object is to provide a new electrolytic developer material.

Yet another object is to provide new sensitizer combinations for photoconductors to assure selective responsive to different light wave lengths or colors.

Various other objects and advantages will become apparent to those skilled in the art from the accompanying description and disclosure.

In accordance with this invention, a photoconductive receptor is utilized as the radiation responsive element of the invention. This photoconductive receptor comprises a suitable substrate or support upon which has been deposited a photoconductor, which photoconductor renders the receptor responsive to light, whereby lightstruck areas are more conductive than the non-light struck areas. The receptor is exposed to a colored light image or pattern. The result is that a differentially conductive pattern is formed upon the receptor corresponding to the image or pattern to be reproduced. Instead of using a uniformly photoresponsive layer on the receptor which is uniformly responsive to same wave lengths, the photoconductive layer of the receptor of this invention is divided into a multiplicity of three selectively light responsive photoconductive areas. These three selectively light responsive areas, which are placed laterally rather than overlying each other on the sheet, are respectively photoconductively responsive selectively to blue, green and red light. These selectively light responsive areas may be placed upon the photoconductive receptor in the form of a pattern of dots, circles, beads spheres, squares, triangles, hexagons, lines, etc. For example, in the case of a selectively light responsive pattern in the form of lines, one line is selectively photoconductively responsive substantially only to blue light. The next adjacent line is selectively photoconductively responsive substantially only to green light, and the next line is selectively photoconductively responsive substantially only to red light. These three line patterns are successively repeated across the surface of the receptor. In the case of dots, beads or geometrical areas, the three areas are in the form of a mosaic or pattern. For example, a repeating series of three differently colored dots or squares are placed in the form of a row across the surface of the receptor. The three differently colored dots are selectively photoconductively responsive, respectively, to blue, green and red light. Similar rows of dots are placed adjacent the first row to form a pattern of many rows and the dots are similarly selectively responsive to blue, green and red light; but, preferably, the dots or squares are staggered in respect to the preceding row so that two dots or squares selectively responsive to the same color are not directly adjacent to each other. Even a random mosaic of the three selectively light-sensitive photoconductive areas may be utilized with success. Each of the different lightsensitive photoconductive areas are made up of a suitable photoconductor, such as zinc oxide, which is sensitized with a different dye or other organic material to make that particular area selectively light responsive to one of the colors, blue, green and red. In addition to the photoconductor and colored light responsive sensitizer, each of the three successive areas contains a different dye visually giving that area a specific subtractive color. The blue sensitized areas are visually colored yellow. The green sensitized areas are visually colored magenta, and the red sensitized areas are visually colored cyan. The dyes or other organic materials utilized for imparting to the photoconductor its particular colored light response are substantially the same in color as the dyes for providing the visual color to the photoconductor or they are used in such small amounts in relation to the coloring dyes that there is no conflict between the dyes, so that the correct subtractive color is visually obtained on the photoconductor.

As a typical method for preparing such a pattern or mosaic, the ingredients of the composition forming a specific area of the mosaic or pattern (including photoconductor, dyes, etc.) are mixed with a suitable organic insulating resinous binder, such as Pliolite (a copolymer of butadiene and styrene), and a small amount of solvent, such as toluene to form a dispersion. Three different dispersions are thus prepared and are then applied in a definite or random pattern, in the form as previously discussed, to the surface of the receptor. The solvent evaporates and the binder affixes the dyed photoconductor. The support or substrate for the dispersion may be any type of self-supporting material, such as plastic, wood pulp paper, cloth, wood, metal, etc., and may be in the form of a plate or in the form of paper-like sheets or films. In some instances, depending on the development technique to be used, a metal substrate or layer is necessary. Preferably, for making color reproductions or prints the substrate is paper or plastic film. The appearance of the completed receptor is a flat surface containing three different colors in the form of dots or lines, etc. which more or less alternate. Preferably, these dots and lines are about 0.001 to about 0.01 inch in width or diameter so that visually the pattern cannot be distinguished without the use of a magnifying glass or microscope.

Upon exposure to a colored light image or pattern, the yellow areas become conductive where struck by blue light; the magenta areas become conductive where struck by green light; and the cyan areas become conductive where struck by red light. Exposure may be effected in a conventional manner, such as by the projection of a colored image from a color positive onto the surface of the receptor by means of a conventional transparency projector and lamp, for a period of time between about 0.001 second and about one minute. Exposure may also be effected with a camera and lens focused on a lighted subject. Successive exposurethrough conventional blue, green and red filters enhances the selectivity of the receptor to the respective colors.

Having been exposed to the color image or pattern, the receptor is differentially conductive in a latent pattern corresponding in intensity and tone to the original color image and is ready for development. Development may be effected either simultaneously with or subsequent to the exposure step. In developing subsequent to exposure, the development is carried out in the dark or in dim light. The development step may involve the imagewise deposition of a white opaque material over the conductive areas, such as by electrolysis or by electrostatic deposition as will hereinafter be discussed in detail. In other words, the white opaque material is deposited on all of the lightstruck areas sensitive to red, green, or blue in proportion to the tone, intensity and hue of the original color. In another modification, instead of depositing a white opaque material on the conductive area the color in the conductive area may be either bleached, reduced or otherwise rendered transparent, colorless, or white. In any event, the development, in essence, comprises removing the color from the conductive areas regardless of the particular color to which each area is responsive.

The result on the receptor is that in an overall area which has been struck by red light, the only colors remaining are the subtractive colors, yellow and magenta. In an overall area struck by green light, the only colors remaining are yellow and cyan. In an overall area struck by the blue light the only colors remaining are magenta and cyan. Since the colors are subtractive, the additive effect of such colors to the eye will not be the desired color, except faintly so; and, therefore, the remaining colors (colorants) are preferably mixed, and this is accomplished by wetting the receptor with a solvent or heating the receptor to fuse adjacent areas so that the remaining colors will diffuse, mix or fuse together over a restricted area. For example, the mixing step mixes the colors over an area of two to four times the area diameter or width of a specific colored area. Upon viewing the receptor after the mixing step, the combination of the subtractive colors results in the correct responsive color in hue and tone to the original light image or light pattern. Thus, in the overall red light exposed area where the cyan has been removed or covered and sealed off from solvent action or fusion, the remaining yellow and magenta colors are mixed together and produce red. In the overall green light exposed area, the remaining yellow and cyan colors are mixed to produce green. In the overall blue light exposed area, the remaining magenta and cyan colors are mixed to produce blue.

The response of the receptor to the light image or pattern is accomplished with the use of a suitable photoconductor. Numerous known photoconductors may be utilized for this purpose, both organic, such as anthracene, and inorganic, such as selenium. Preferably, these photoconductors are inorganic and substantially insoluble in the solvents and dyes utilized. Usually, the inorganic photoconductors are utilized in particulate form as a very fine powder and are preferably white or light colored. Generally, the average diameter of the photoconductor particle is between about 0.1 and about 1 micron. Preferred inorganic photoconductors include zinc oxide, indium oxide, cadmium sulfide, lead sulfide and mercuric oxide.

Since photoconductors vary considerably in their photoconductivity upon exposure to light and also in their resistivity in the dark, the particular photoconductor to be utilized will depend to some extent upon the type of development procedure to be employed. For example, in electrolytic development of the colored image, the photoconductor should have a relatively high conductivity upon exposure to light since a minimum resistance exhibited by the photoconductor is desirable for electrolytic development. In general, for electrolysis the photoconductor must have a photoconductivity or conductivity upon exposure to light of at least mho/ cm. (measured in an electrolytic cell with an 0.8 mil zinc oxide coating and extrapolated to a cubic centimeter). The dark conductivity (dark adapted conditions) of such a photoconductor will be 10 to 100 times less or even less than the conductivity in the light. When particulate photoconductors are used and development is to be accomplished by electrolysis, the

particles of the photoconductor should be substantially in direct contact with each other as well as with a conductive support or the substrate, such as metal, in order to provide the minimum of resistance to current passage between particles and subtrate. When electrostatic development procedure is to be employed, it is preferable to use photoconductors having a relatively high resistivity or low conductivity in the light and consequently a very high resistivity in the dark. Thus, for electrostatic development the photoconductor will usually have a photoconductivity of 10- to 10* mho/cm. upon exposure to light. Zinc oxide may be utilized for both types of development procedures depending on the light conductivity of the zinc oxide.

As previously stated, dyes are utilized in combination with the photoconductor as a selective colored light sensitizer and as a colorant for the mosaic surface areas. In general, the dyes actually color the surface or particle of photoconductor. No binder or resin is needed to hold the dye to the surface of the photoconductor. These dyes should be such that there is substantially no chemical reaction between the dye and the photoconductor which would interfere materially with the photoconductive properties of the photoconductor. In addition, the dyes should be capable of being bonded to the photoconductor in some manner. For example, bonding may be achieved between the dye and photoconductor by ligand formation, by adsorption, or by chemical bonding, which type of bonding is inherent in the dye itself.

Selective colored light sensitizing dyes or other organic materials for photoconductors are known in the art. Suitable dyes capable of selectively sensitizing the photoconductor, such as zinc oxide, to red light include the triphenylmethane dyes, Patent Blue V (C.I. 42045), Victoria Blue B (C.I. 440445), Xylene Cyanole FF (C.I. 42135), Alphazurine 2 G (C.I. 42045), and Pantacyl Brilliant Blue A (C.I. 42080). Suitable dyes for selectively sensitizing the photoconductor to green light include the exanthene dyes, Pyronine B (C.I. 45010), Phloxine B (C.I. 45410), Rhodamine G (C.I. 45150), Rhodamine B Base (C.I. 45170), and Violamine (C.I. 45190); the azine dyes, Methylene Violet (C.I. 50205) and Neutral Red (C.I. 50040); and the cyanine dye, Astrophloxine FF (C.I. 48070). Suitable dyes for selectively sensitizing the photoconductor to blue light include the yellow dye, 3-carboxymethyl 5 (3 ethyl 2(3) benzothiazoylidene) rhodamine-triethylamine salt, the diphenylmethane dye Auramine (C.I. 41000), the thiazole dye, Seto-Flavine-T (C.I. 49005), and the acridine dye Acridine Yellow (C.I. 46025).

The amount of sensitizing dye utilized is usually between about 0.00025 and about 0.25 weight percent based on the photoconductor. In general, the amount of sensitizing dye will depend upon the particular sensitizing dye, the coloring dye used in combination therewith, and the kind and type of photoconductor.

Dyes for providing the subtractive colors to the mosaic areas are also known in the art. Suitable dyes for providing the color cyan include Helvetia Blue (C.I. 42780), Azosol Fast Blue GLA (C.I. 50320), Sudan Green 4 B (C.I. 615615), Anthraquinone Blue Sky Base (C.I. 62100), and Wool Green (C.I. 44090). Suitable dyes for providing the magenta colored mosaic include Sudan Red BBA (C.I. 26105), Magenta ABN (C.I. 42520), Rhodamine B (C.I. 45170), Oil Red-O (C.I. 26125) and Magenta RV (a-Quinacridine). Suitable dyes providing yellow color to the mosaic include Calcozine Yel-low OX (C.I. 41000), National Oil Yellow 2625 (C.I. 11020), Sudan Yellow GRA (C.I. 21240), FDNC Yellow No. 4 (C.I. 11390), and Quinoline Yellow (C.I. 47005). Some dyes are useful for both light sensitization and coloring the pattern. However, in most instances, an additional coloring dye is utilized for coloring purposes even though the color sensitizer is also useful as the coloring dye.

'An amount of coloring dye between about 0.01 and about 0.2 weight percent based on photoconductor is satisfactory, the actual amount depending on the depth of color desired.

The dye sensitizers may be used singly or in combinations of two or more dyes. The same applies to the colorants. The dyes are appliedsingly or in combination to the photoconductor dispersion or to the photoconductive layer in solvent, such as ethyl acetate or methyl alcohol.

As previously mentioned, insulating resinous binders are utilized to bond the colored or dyed photoconductor particles together as well as to bind the resulting photoconductive layer to the supporting surface. The preferred resinous bonding agents are those which are no more conductive than the photoconductor under dark adapted conditions. When the receptor is to be developed by the electrolytic technique, the resinous binder should also preferably have a low degree of wettability toward the photoconductive particles as well as being substantially water insoluble so that the binder mainly collects in the interstices between particles and does not usually form a complete film around the photoconductive particle. Suitable binders include the copolymer of styrene and butadiene (in a weight ratio of 70:30 to 85:15) known as Pliolite, polystyrene, chlorinated rubber (Parlon), polyvinylchloride, Saran (polyvinylidene chloride), nitrocellulose, and polyvinylbutyral. Pliolite is a particularly useful binder to be used when the receptor is to be developed by the electrolytic method. The weight ratios of binder to photoconductive particles generally range from 1:10 to 1:1, preferably 1:6 to 1:3.

In preparing the photoconductive layer, mixtures of two or more photoconductors may be utilized. Similarly, two or more binders may be used in admixture. Also, inert fillers or pigments, such as titanium dioxide and barium sulfate, may be admixed with the photoconductor or binder.

Quite generally, increasing amounts of sensitizer (per unit weight photoconductor) increases the sensitivity, but it levels off beyond a certain point, presumably due to adsorption saturation and light-filtering action of the dye.

Generally speaking, as the tint strength of the color in the ZnO dispersion is increased, the light sensitivity decreases, and in many cases the spectral response shifts in proportion to the increase. Lighter tints of magenta, cyan, and yellow with good sensitivity and selectivity are easily obtained, but the same with strong tints is more diflicult. By adding more of the sensitizers to the colored dispersions, it is possible within limits to adjust the exposure times of all three to approximately the same value.

The following methods are useful in preparing various types of colored mosaics or patterns on the receptor in accordance with this invention. One method is the successive silk screening or spraying of three different colored dispersions through a stencil which has a regular pattern of openings such that for each successive spraying operation the same stencil can be used in a slightly different position. The result is that the three dispersions are inter: layered between each other without appreciable overlapping. These dispersions included the photoconductor, appropriate dyes, binder and a solvent. Etched metal foil stencils, such as copper, can also be used in place of a silk screen for this purpose.

A gravure-type printing plate having patterns similar to the stencil is useful in another method of forming the mosaic or pattern. The three patterns are interlaid on the same surface by transferring the three colored dispersions from the cavities in the plate.

Several methods employing the use of uniform coatings of essentially unsensitized particulate photoconductor, such as ZnO, have been found to be satisfactory for forming the mosaic. In one method, the sensitizing and coloring dyes in solution are wiped or sprayed through stencils in three successive interlaying steps onto a photoconductive coating, already laid down and bonded to the receptor. In another method, dark adapted ZnO coatings bonded to a suitable metal layer or support are exposed with light through photographic screens and the different sensitizer and color, dyes laid down by electrolysis or electrostatic technique. Repeating the procedure three times with different color compositions, the interlaid pattern is produced. Also, the sensitizer and color dyes can be printed onto the photoconductive surface in an inter- ]aying pattern by conventional gelatin duplicator technique or spirit duplicator, or other conventional printing processes such as gravure, letter press, and lithography.

Stripe or line patterns may be drawn by hand on metal and paper surfaces as repeating triplets of parallel lines of the three dispersions. Also, a sheet of paper or metal foil may be wrapped around a cylinder and placed in a lathe. A motor-driven hypodermic syringe mounted on the lathe carriage ejects a small stream of photoconductor dispersion containing the appropriate dyes onto the sheet on the cylinder while the lathe performs an operation similar to threading. A sufliciently large space is left between the lines to interlay the other colored dispersions as similar lines.

Another method uses a rectangular block of metal having 50 or more fine grooves per inch milled almost across the entire surface of one side of the block. On the opposite surface of the block is cut three reservoirs and at right angles to the fine grooves on the lower surface and of such depth that the first reservoir is connected to every third fine groove below; the second reservoir to every fine groove on one side of those that connected to the first reservoir; and the third reservoir connected to the remaining fine grooves. This grooved surface is laid on the sheet to be coated. On pouring the three colored dispersions of the photoconductor and dyes into the three reservoirs, respectively, and moving a sheet of metal or paper parallel to the grooves, an interlaid striped mosaic Coating is automatically produced.

In still another method, three colored dispersions containing photoconductor, resin binder and dyes can be made into the form of fine dry beads or balls. This is accomplished by separately spray drying the dispersions in a conventional manner to form beads of about 0.001 inch in diameter. The fine beads of different color are mixed. Paper or metal foil is soaked or dampened with a solvent, such as toluene, and the damp substrate is then dipped into the dry beads and removed whereby a close packed adherent monolayer of beads is attached to the surface of the substrate. The resulting sheets can be used in this form for production of colored images by the electrostatic development method, or the beads can be softened by solvent and heat and then flattened by presslng into a smooth surface suitable for use in the electrolytic development method as hereinafter described.

If one of the photoconductor dispersions is sprayed from a paint gun onto a metal surface using the technique of electrostatic spraying and the spraying is stopped when about one-third of the metal surface is covered with fine droplets of the dispersion, the spraying of the second dispersion will, under these conditions, place its droplets mostly between those already on the metal plate, and similarly with the third dispersion. Drying is carried out between spraying steps. In this way a random mosaic is created.

Aqueous emulsions of an internal phase of photoconductor dispersion containing Water-insoluble dyes and binder and an external phase of water can be prepared. Three such emulsions representing the three different colored coating dispersions can be prepared, mixed and coated on metal foil in a layer thin enough to produce essentially a monolayer of emulsion droplets. On drying this produces a random color adherent mosaic.

It is important to note that almost any type of mosaic,

Well made, or badly made, on paper or on metal will produce images by the electrostatic development technique. The electrolytic development technique, however, must be performed with coatings on good conductors such as metals and without bare spots or pin holes where the metal is exposed and the particles of photoconductor should contact each other and the metal layer to assure a conductive path in light-struck areas. A thin gelatin layer or film may be placed over the mosaic pattern as a protective surface and as a means of aiding electrolytic development, especially when the gelatin layer contains an electrolyte.

The photoconductive receptor of this invention is suitable for reproduction of a color image by exposure of the receptor to a color radiation pattern or light image, usually of the three primary colors. As a result of exposure to the radiation pattern or light, a differentially conductive pattern is formed on the receptor surface by virtue of the increased conductivity of the photoconductor in the light-struck areas of the mosaic. The difference in conductivity of the fully irradiated areas as compared to the non-irradiated areas is at least 10 times and generally as much as 100 times or greater.

In one embodiment of this invention in which the exposed receptor is electrolytically developed, the surface of the exposed receptor is contacted with a solution containing an electrolyte and an electric potential is applied between the receptor and the developer solution. In this type of development the receptor contains a conductive layer, such as a metal layer, as the support for the photoconductive layer. The conductive layer, such as a metal layer, of the receptor is connected to source of direct current or grounded, and the electrolytic solution is connected to the opposite potential of the direct current. A voltage is impressed across the electrolytic solution and the conductive layer of the receptor while the receptor is in contact with a developer material which results in the reproduction of the image or pattern by deposition of developer material on the conductive areas of the receptor. This may be done simultaneously with the exposure step, or as a subsequent step since the receptor sheet, particularly in the case of zinc oxide, has a useful memory of as much as several minutes. In some instances, the developer material is dissolved in the aqueous electrolyte solution and itself constitutes the electrolyte and no added electrolyte is necessary. In other instances, the electrolyte liquid or solution by virtue of its source will contain an electrolyte. In case it is necessary to add an electrolyte to the solution, suitable electrolytes, such as sodium chloride, sodium carbonate, sulfuric acid, acetic acid or sodium hydroxide, may be used.

The development may be carried out either anodically or cathodically, depending upon the type of photoconductor on the surface, the receptor construction, and the kind of developer material used. In other words, the receptor may be connected to the positive or negative source of direct current without departing from the scope of this invention.

In such electrolytic development, a suitable developer material is dissolved or suspended in water and the surface of the receptor contacted with the aqueous electrolyte medium, such as by inserting the receptor in a vessel containing the aqueous medium or by brushing the aqueous medium on the surface with a sponge or gelatin roller or the like, which is connected to a direct current source.

An example of a suitable combination of developer material and aqueous electrolyte is an aqueous latex or suspension or emulsion containing negatively or positively charged polymer or resin particles containing a white pigment, such as titanium dioxide or zinc sulfide. Examples of solid polymers or resins which are positively charged in aqueous medium and, therefore, are useful as a component of an aqueous electrolyte solution when in suspension or emulsion for cathodic development include a polymer of a fatty acid and a polyamine (Versamid), a

copolymer of vinyl chloride and vinyl acetate, polyvinyl acetate, silicones and epoxy resins. Examples of solid polymers or resins which are negatively charged in aqueous medium and, therefore, are useful as a component of an aqueous suspension or emulsion for anodic development include, nylon, polyethylene, chlorinated rubber, polybutadiene, a copolymer of butadiene and styrene (Pliolite), and acrylic polymers and copolymers. Some of such polymers or resins may be sufficiently white in color and opaque that an added white pigment is unnecessary. During electrolysis, the charged white particles are deposited selectively on the latent image or conductive pattern during electrolysis.

When using zinc oxide as the photoconductor, the receptor is usually made the cathode in the electrolytic process for best results because of the rectifying efliect of the zinc oxide-electrolytic solution interface. With zinc oxide, a particularly useful developer material includes dissolved Versamid and suspended titanium dioxide in an aqueous electrolyte solution. Versamid 100 is a low molecular weight polymer of a fatty acid and a polyamine-HCl which is soluble in water. It is semi solid at room temperature, melts at 43 -53 C. and has an amine value of 83-93. About 1 to 2 percent by weight of the Versamid is used in a dilute aqueous acid solution. About 1 to 10 percent by weight of titanium dioxide based on water is suspended in the solution. The particle size of the titanium dioxide is between 0.1 and 0.4 micron in average diameter but may exist as larger agglomerates in suspension. During electrolysis, the lightstruck areas of the receptor surface which are conductive become alkaline because of the evolution of hydrogen. The Versamid 100 will precipitate in the alkaline areas of the receptor and the titanium dioxide will adhere to the precipitated Versamid 100 forming white areas.

In a modification of the electrolytic development procedure when using zinc oxide as the photoconductor, the latent image is first cathodically developed using an aqueous electrolyte solution containing a soluble metal salt, such as silver nitrate or copper sulfate, whereby metal is electrolytically deposited in the light-struck areas which serve as the cathode. Thereafter, in a second development step, the developed receptor from the first development step is subjected to a second electrolytic development, but in this second development an anodic system is used in which the aqueous electrolyte solution contains negatively charged water-insoluble white polymer particles in suspension or in emulsion. The negatively charged particles deposit on the metal plated areas formed by the first development, which areas are now the anode of the system. In this manner, the normal rectifying effect of zinc oxide in an anodic system is overcome because of the metal surface on the zinc oxide formed in the first development step.

The current density necessary for development by electrolysis is usually between about 1 and about 100 milli amperes per square centimeter. In general, the voltage required to give such a current through the electrolytic solution and receptor is between about 3 and about 200 volts, usually between 10 to 60 volts per mil thickness of coating. The time required to produce the visible deposit of the developer material by electrolysis is between about 0.1 second and about 1 minute depending upon the current and the developer material utilized.

Another method of carrying out the reproduction process in combination with electrolytic development is the use of dyes for the cyan, magenta and yellow colors which are bleachable or reducible upon electrolysis. There are numerous dyes of this type which give the appropriate colors. These dyes are, for example, the triphenylmeth'ane dyes and azo dyes, such as those disclosed in US. Patent No. 2,470,769, issued May 24, 1949, and US. Patent No. 2,612,496, issued September 30, 1952. Typical examples of bleachable magenta dyes include the triphenyl methane dye, Fuchine (C.I. 42510), and the azo dye, Azosol Fast Red BE (CI. 12715); Examples of suitable bleachable cyan dyes include the triphenyl methane dye, Victoria Blue BA base (C.I. 44045B) and the azo dye, Indoine Blue 3 B (C.I. 12210). Examples of bleachable yellow dyes include the diazo dye, Brilliant Yellow C (CI. 24890), and the azo dye, Bismark Brown R (CI. 21010). The above azo dyes are reducible in aqueous ethyl alcohol containing zinc chloride as the electrolytic solution. The dyed areas struck by light will be reduced to white or transparent upon electrolysis.

The metal layer, when used in the receptor for electrolytic development, may be sufficient as a self-supporting layer for the photoconductive layer of the receptor or may be bonded or aflixed to a backing for support or insulation purposes. Foils or films of metal are suitable as a self-supporting metal layer. When a backing is utilized, the metal is deposited upon the backing or adhered thereto in the form of a continuous film or foil. The metal layer can be deposited on the backing by vapor deposition, electro-plating, precipitation, lamination of metal foil, or by bonding metal particles thereto with a suitable binder. Conductance of the metal layer is important since the metal layer is used as the conductor to one of the electrodes of the direct current source during electrolytic development. Therefore, the metal layer should offer no more lateral or surface resistance than about 1,000 ohms, preferably no more than ohms per square, for electrolytic development. The thickness of the metal layer, of course, will depend upon whether it is the support itself or whether it is utilized merely as the conductor. When the metal layer is utilized upon a nonconductive backing, the thickness of the metal layer is usually between about 0.1 and about 25 microns. Suitable backing material for this metal layer is wood pulp paper, rag content paper, glass, and plastic films, such as cellulose acetate films, Mylar films, polyethylene films and polypropylene films. Even cotton or wool cloth may be utilized as the backing without departing from the scope of this invention. Suitable metals for the metal layer include aluminum, tin, magnesium, chromium, silver and copper; preferably aluminum.

The development of the latent colored image may also be effected electrostatically as well as electrolytically. The electrostatic methods of developing reproductions are known in the art. In this method, the development is achieved by selectively attracting or depositing charged particles to the image surface. In the case of this invention, these particles would be white and may contain an electrostatic type resin which is fixed to the surface by heating or solvent action. In the electrostatic process either the exposed areas are charged or the nonexposed areas are charged. Charging of the exposed areas is achieved by creating an electrical potential between the exposed receptor and an electrode or plate. Charging the non-exposed areas is achieved by precharging the receptor prior to exposure. precharge is dissipated upon exposure. Thereafter, charged particles, either of the same charge or of the opposite charge as the paper, depending upon which areas of the receptor are charged, are utilized. The latent image in the form of a charge is brushed, sprayed or treated with charged particles. The charged particles will be retained imagewise on the surface in either of the above cases as a positive or negative, depending upon the charge. Thereafter, the receptor may be heated or treated with a solvent or sprayed with a lacquer to firmly affix the white particles to the surface. The result is similar to the electrolytic process of development.

A variation of the electrostatic process is the use of a corona discharge on the exposed receptor. In this case, a corona electrode is spaced at an appropriate distance from the exposed receptor and a high potential is made between the corona discharge and the receptor. Be tween the electrode and the receptor the appropriate white particles are sprayed or dusted or otherwise in- In the exposed areas, the

troduced therebetween. The corona discharge forces the White particles to the exposed areas of the receptor. As in the electrostatic process, the exposed particles may contain a suitable resin which, upon heating or solvent action, firmly affix themselves to the receptor surface.

After development, the unwanted color is blotted out by the white overlying fixed layer or is destroyed. The remaining colors reproduce a colored image but the color of the image after development may be off-color and is somewhat faint. To bring forth a strong and true image from the subtractive colored areas remaining on the receptor, the remaining colored areas are mixed over a restricted area. In other words, two to four adjacent colored areas are treated to cause mixing of the subtractive colors in these areas. This is accomplished by washing or moistening the image surface of the receptor with a suitable solvent for the dyes giving the subtractive colors. The binder used for applying the white covering or masking layer should be substantially insoluble in this solvent. Suitable solvents for this purpose are methyl alcohol, ethyl alcohol, toluene and ethyl acetate. The solvent may be conveniently applied by spraying a thin film of solvent on the image surface of the receptor and drying. The resulting image is true and strong because a true subtractive color process has now been effected by the mixing of the subtractive colors.

The white coating on the unwanted color area protects that area from the solvent and thus the unwanted color is not mixed with the remaining colored areas. In case the dye in the unwanted colored area is destroyed, there is no color to mix with the remaining colored areas. In either case, the unwanted color does not interfere during the solvent treating step in producing a true color reproduction.

As a means for better understanding of the present invention, the following drawings diagrammatically illustrate a typical receptor construction. FIGURE 1 is a diagrammatic illustration of a receptor suitable for both electrolytic and electrostatic development. Element 11 is the base of the receptor which may be paper or plastic film or other suitable insulating sheet material. Element 12 is a thin film of metal, such as aluminum foil, or vapor deposited aluminum, affixed upon base 11. On top of metal layer 12 is deposited the mosaic of the photoconductor containing in combination therewith the appropriate dyes to achieve the mosaic of red, green, and blue light responsive areas as previously described and shown in the drawing.

FIGURES 2 and 3 of the drawing illustrate two stages of developing the latent image. In the three figures, Y is the color yellow and represents an area sensitive to blue light only. M is the color magenta and represents an area sensitive to green light only. C is the color cyan and represents an area sensitive to red light only. The subscripts on the color indicators represent the type of light to which that area is sensitive. Thus, r represents red, g represents green, and b represents blue.

As an example of the operation of this invention, the receptor surface of FIGURE 1 is exposed to a colored image by focusing the image on the surface with suitable lenses. That portion of the image exposed to red light is electrolytically developed with a white pigment, such as titanium dioxide, and a binder. From exposure to red light, areas C become more conductive while areas Y and M remain substantially unchanged in conductivity. The exposed surface is then electrolytically developed by connecting metal layer 12 of FIGURE 1 to the cathode of an electrolytic cell containing a solution of an electrolyte and a binder, such as Versamid and suspended titanium dioxide. The Versamid 100 is precipitated from solution onto areas C The titanium dioxide suspension adheres to the Versamid on areas C thus covering the cyan color and rendering the C areas white as shown in FIGURE 2. Thereafter, the receptor is removed from the electrolytic cell and dried. The partially developed surface is then moistened with a solvent, such as methyl alcohol, for the dyes M and Y. This results in mixing of the dyes in areas M and Y producing the color red by the subtractive phenomenon as shown in FIGURE 3. The receptor is dried and the finished reproduction is obtained. The image surface may then be treated with lacquer, wax or other protective surface, if desired, without departing from the scope of this invention. The color reproduction thus obtained is very stable to light with substantially no fading of the colors over an extended period of time.

The following examples are offered as a better understanding of the present invention and are not to be construed as unnecessarily limiting thereto.

EXAMPLE 1 A suspension of the photoconductor and insulating resin was prepared by mixing 1680 grams of a 30 percent solids toluene solution of Pliolite (a copolymer of styrene and butadiene), 1104 grams of toluene, and 2016 grams of zinc oxide (having a photoconductivity of at least mho/cm.). The mixture was then blended in a Waring blender with the appropriate dyes and colorants. The mixing in the Waring blender was accomplished by first adding the Pliolite solution followed by adding the toluene and stirring the mixture slowly. During the slow stirring, the zinc oxide was sifted in slowly. After the entire mixture had been placed in the Waring blender, the blender was turned to high speed and stirred for at least minutes. The temperature of the mixture must be maintained below 160 F. during mixing.

About 0.75 cc. of a 0.2 percent solution of the super sensitizer, Seto-Flavine-T in methanol was next added to the blender. Seto-Flavine-T is normally a selective sensitizer for blue light; however, when used in combination with other color sensitizers it acts to increase the sensitivity of the other sensitizers to their respective light sensitivity because of a synergistic effect. Thereafter, the proper selective color sensitizing dye was added. In this case, to the above was added 0.5 cc. of a 0.2 percent solution of Alphazurine 2 G in methanol per 100 grams of dispersion to make the mixture responsive to red light. Mixing was continued until the dispersion passed a 400 mesh screen. Preferably, the color sensitizing dye is not added until the yellow color of the Seto-Flavine-T has substantially disappeared which was done in the above case. At 150 F. the color disappeared in about 10 minutes of mixing. At lower temperatures, as much as 24 hours are required for the disappearance of the yellowing color of the super sensitizing dye. Somewhat improved results were obtained by using lower temperatures and longer times for disappearance of the yellow color of the Seto-Flavine-T. When the color sensitizing dyes are added, the temperature should be maintained less than 90 F.

After the color sensitizing dye is added, as above, the coloring dye is added. Therefore, in the above admixture using Seto-Flavine-T and Alphazurine 2 G, the cyan dye, Sudan Green 4 B, was added to the dispersion and thoroughly mixed therewith in the Waring blender while maintaining the temperature below 90 F. A suificient amount of the cyan dye was added to obtain the desired density of color in the mixture, the amount being about 4 to 5 grams of the coloring dye.

The above procedure was repeated for a second batch in which 0.5 cc. of a 0.2 percent solution of Phloxine-B in methanol per 100 grams of dispersion was added to the initial zinc oxide mix containing the super sensitizer to make this batch sensitive to green light. After proper mixing as above described, approximately 5- grams of Rhodamine-B and 2 grams of Sudan Red BBA and 40 grams of Magenta RV were added to give the dispersion the magenta color with green sensitization. A third dispersion was prepared as above with 1.5 cc. of a 0.2 percent solution of yellow 454 dye, 3-carboxymethyl-5-(3- ethyl-2 (3 -benzothiazolyidene) rhodamine triethylamine salt, per 100 grams of dispersion by adding to the initial mixture of zinc oxide and super sensitizer in accordance with the above procedure to sensitize the mixture to blue light. To this third dispersion was then added the yellow coloring dyes Sudan Yellow GRA and Yellow No. 4.

The dispersions were then ready for separate application to a base material or support. In this example, these dispersions were added as lines through a hypodermic syringe to aluminum foil rotating on a lathe. The first line was added at a rate of 2 feet per minute and dried at a temperature of to F. Similarly, the second and third lines of a different color were added so that the entire metal foil was completely covered with the three different colored lines. The aluminum foil should be clean and free of grease and dirt. In addition, it is preferred to wash the aluminum foil prior to depositing the mosaic thereon with an aqueous solution of potassium hydroxide to remove any aluminum oxide on the surface.

The above sheet is then dark adapted for about onehalf hour at F. The completed receptor was then exposed for one second toa Kodachrome colored transparency projected thereon with a 300 watt General Electric Projection Lamp. Thereafter, the sheet was connected to the negative electrode of a 50 volt direct current potential and placed in an electrolytic solution containing 1 percent Versamid 100 admixed with suspended titanium dioxide in an amount of about 3 weight percent based on water. The positive electrode of the DC. source was connected to the electrolytic solution. Approximately 2 m-illiamps of current were passed three seconds whereby titanium dioxide was deposited on the latent image. The receptor was then removed from the electrolytic solution and dried at about 150 F. A light colored reproduction of the original Kodachrome transparency was obtained on the receptor.

Similar results have been obtained by printing mosaic of the three different dispersions with a stencil in which the stencil was small squares and the ultimate mosaic was a brick work of squares of the three different colors.

Similarly, results have been succssful in partially drying the three different dispersions by spraying in warm air to form small beads. These beads were spread as a monolayer in admixture over the surface of the receptor. The beads were then pressed slightly and dried. The receptor was then exposed and developed as above resulting in a good color reproduction. The receptor, in a horizontal position, was then sprayed with ethyl alcohol and allowed to air dry. The image was much stronger in color after the solvent treatment. The color reproduction and definition of the image was good.

EXAMPLE 2 The following Table I shows three different combinations of dyed dispersions which have been found to be useful in making the zinc oxide receptor of Example 1. Exposure and development of colored images was successful with these combinations as illustrated by Example 1. Dispersions A, B and C amounted to 400 grams each and contained zinc oxide, Seto-Flavine-T, Pliolite binder and solvent in proportions as shown in Example 1. In addition, dispersion A contained about 2 cc. of a 0.2 percent solution of Alphazurine 2 G in methyl alcohol as a red light sensitizer. Dispersion B contained about 2 cc. of a 0.2 percent solution of Phloxine B in methyl alcohol as a green light sensitizer, and dispersion C contained about 5 cc. of a saturated solution of Auramine in methyl alcohol as a blue light sensitizer.

Table I Combination Cyan dispersion, red sensitized Magenta dispersion, green sensitized Yellow dispersion, blue sensitized Stolvent intlast reating ep 1 Dispersion A, 400 grams Dispersion B, 400 grams. Dispersion C, 400 grams I-Ielvetia Blue (Cyan dye), 0.5 Rhodamine B base (Green. light Yellow 454 soln.* (Blue light sensi gram. sensitizer), 003 gram. tizer), cc. Ethyl alcohol.

Sudan Red BBA (Magenta dye), Caleozine Yellow 0X (Yellow dye),

0.3 gram. 0.5 gram.

2 Dispersion A, 400 grams Dispersion B, 400 grams Dispersion O, 400 grams 50-50 mixture:

Azosol Fast Blue GLA (Cyan Rhodamine B base (Green light Yellow 454 s0ln.* (Blue light sensi- Ethyl alcohol,

dye), 0.4 gram. sensitizer), 004 gram. tizer), 18 cc. methyl ethyl Magenta ABN (Magenta dye), 0.4 National 0' Yellow 2625 (Yellow ketone;

gram. dye), 0.7 gram.

3 Dispersion A, 400 grams Dispersion B, 400 grams Dispersion O, 400 grams Anthraquinone Blue Sky Base Rhodamine 13 base (Green light Yellow 454 soln.f (Blue light sensi- (Cyan dye), 0.5 gram. sensitizer), 0.05 gram. tizer), cc. Ethyl alcohol.

Oil Red-O (Magenta dye), 0.35 gram. Quinotine Yellow (Yellow dye),

0.8 gram.

*Saturated solution in methyl alcohol.

EXAMPLE 3 The receptor sheet of this example was coated by the stripe method in the manner and with the apparatus described in Example 1. The photoconductor used was zinc oxide colored and sensitized with dyes to give the stripes both their proper color and approriate selective color sensitivity as shown in Example 1. The receptorsheet material was removed to a dark room and placed beneath a small projector similar to a photographic enlarger. The sheet'was laid on a metal plate about a foot square, which is connected to the positive terminal of a direct current high voltage power supply. The sheet was charged by passing a corona wire electrode over the surface at a distance of about 1 /2 inches. The corona electrode was connected to the negative terminal of the high voltage power supply. The corona wire electrode was constructed as a wand. The wire electrode was .005 inch in diameter and 10 inches long suspended on studs on a /2 inch diameter plastic rod. The rod handle was fitted with sheet plastic feet which also served as guides when the wire was passed over the sheet in the charging operation. A potential of about 15,000 volts was applied to the electrode. The charged sheet was then exposed. The exposure time was A second. The image was projected from a 35 mm. Kodachrome transparency. The projector was a modified Leitz 35 mm. unit with an optical condensing system and a 150 watt projection lamp. The lens is an 1735-50 mm. unit but was stopped down with a diaphragm to approximately f/ 8. The image was focused at a distance of 18 inches from the projection lens. The exposure was timed by applying power to the lamp with a timer of the synchronous motor driven switch type.

The exposed sheet was then treated to develop the image. The sheet was placed in a shallow tray which contained the developing toner and carrier. The tray was rocked end to end to cause the powder to cascade over the sheet depositing the white toner on the image. The powder system was selected so as to produce an image from a positive light image. The white toner was deposited on the light-struck areas of the image to produce a reproduction of the original image. In this case, the powder system consisted of a fine powder of Saran resin (polyvinylchloride) pigmented with white titanium dioxide (this is the toner which is deposited on the image), and aluminum oxide carrier for the toner which causes it to flow and also imparts the proper triboelectric charge tothe toner. In this case, the particle size of the carrier was about 100 mesh. The sheet was removed from the developing tray and the loose and excess developing material shaken off. The lights were then turned on so as to see the resulting print.

The balance of the procedure was carried out in room light. The remaining step was to fix the print. That is, the toner had to be treated so that it could not be smudged. This was accomplished by heating the sheet briefly to make the Saran resin tacky and attach itself to the print surface. Thereafter, the fixed sheet was sprayed with ethyl alcohol to bring out the color resulting in a good color reproduction.

Another modification of the fixing step is to spray the print with lacquer. The protective film of lacquer will also give the print a desirable gloss.

When fixing the print with the lacquer, it is possible to achieve the color fusion previously mentioned if the correct solvent (in this case alcohol) is included in the lacquer formula. The lacquer solvents dissolve some of the color in the zinc oxide coatings which then run together to a limited extent. The viscosity of the lacquer film keeps the image from running or bleeding.

Various alternative dyes and dye combinations as well as various photoconductors will become obvious to those skilled in the art without departing from the scope of this invention.

Having described our invention, we claim:

1. A color reproduction receptor comprising a support and an image receptive lamina comprising a dark adaptable photoconductor which is photochemically stable at room temperature bonded to said support in the form of a plurality of three coplanar, laterally disposed, subtractively colored surface areas substantially coterminously adjacent one another, said subtractively colored surface areas being separately and visually colored cyan, magenta and yellow and said cyan, magenta and yellow colored surface areas being selectively sensitive to red, green and blue light, respectively.

2. A color reproduction receptor comprising a support and an image receptive lamina comprising a dark adaptable, inorganic particulate photoconductor which is photochemically stable at room temperature bonded to said support in the form of .a plurality of three coplanar, laterally disposed, subtractively colored surface areas substantially coterminously adjacent one another, said subtractively colored surface areas being separately and visually colored cyan, magenta and yellow with a correspondingly colored dye and said cyan, magenta and yellow colored surface areas being'selectively sensitive to red, green and blue light, respectively, with a different correspondingly sensitive dye.

3. A color reproduction receptor comprising a paper backing, a metal layer overlying and affixed to said paper backing and an image receptive lamina comprising an admixture of a dark adaptable photoconductor which is photochemically stable at room temperature and an insulating organic resinous binder bonded-to said metal layer in the form of a plurality of three coplanar, laterally disposed, different visually subtractively colored surface areas substantially coterminously adjacent one another, said three different subtractively colored surface areas separately containing at least one cyan dye, at least one magenta dye and at least one yellow dye,

and in addition separately containing at least one red light-sensitizing dye in the cyan colored surface area, at least one green light-sensitizing dye in the magenta colored surface area, and at least one blue light-sensitizing dye in the yellow colored surface area.

4. The receptor of claim 3 in which said photoconductor is zinc oxide in particulate form.

5. The receptor of claim 4 in which said metal layer is an aluminum layer.

6. A color reproduction receptor comprising a paper backing and an image receptive lamina comprising an admixture of a dark adaptable photoconductor which is photochemically stable at room temperature and an insulating organic resinous binder bonded directly to said paper in the form of a plurality of three coplanar, laterally disposed, different visually subtractively colored surface areas substantially coterminously adjacent one another, said three different subtractively colored surface areas separately containing at least one cyan dye, at least One magenta dye and at least one yellow dye, and in addition separately containing at least one red lightsensitizing dye in the cyan colored surface area, at least one green light-sensitizing dye in the magenta colored surface area, and at least one blue light-sensitizing dye in the yellow colored surface area.

7. The receptor of claim 6 in which said photoconductor is zinc oxide in particulate form.

8. A receptor comprising a backing and a dark adaptable photoconductive lamina which is photochemically stable at room temperature affixed to said backing, said photoconductive lamina having a plurality of coplanar, laterally disposed, different subtractively colored surface areas substantially coterminously adjacent one another, containing respectively different combinations of at least two materials selected from the group consisting of a cyan colorant and a sensitizer capable of rendering said photoconductive surface area sensitive to red light, a magenta colorant and a sensitizer capable of rendering said photoconductive surface area sensitive to green light, and a yellow colorant and a sensitizer capable of rendering said photoconductive surface area sensitive to blue light.

9. A process which comprises photographically creating a differentially electrically conductive pattern on a color reproduction receptor comprising a support and an image receptive lamina comprising a dark adaptable photoconductor which is photochemically stable at room temperature bonded to said support in the form of a plurality of three coplanar, laterally disposed, subtractively colored surface areas substantially coterminously adjacent one another, said subtractively colored surface areas being separately and visually colored cyan, magenta and yellow and said cyan, magenta and yellow colored surface areas being selectively sensitive to red, green and blue light, respectively, and rendering colorless or white the more conductive areas of said differentially conductive pattern.

10. A method for making a colored reproduction of a colored image which comprises exposing to a colored light image a color reproduction receptor comprising a support and an image receptive lamina comprising a dark adaptable inorganic particulate photoconductor which is photochemically stable at room temperature bonded to said support in the form of a plurality of three coplanar, laterally disposed, subtractively colored surface areas substantially coterminously adjacent one another, said subtractively colored surface areas being separately and visually colored cyan, magenta and yellow with a correspondingly colored dye and said cyan, magenta and yellow colored surface areas being selectively sensitive to red, green and blue light, respectively, with a different correpondingly sensitive dye, to form a differentially electrically conductive pattern corresponding to said light image, electrostatically depositing an electrostatic developer powder comprising a resin and a white pigment on the conductive areas of said differentially conductive pattern, and fixing said electrostatic developer powder on said receptor.

11. A method for developing a colored reproduction of a colored image or pattern which comprises rendering white the more conductive areas of a differentially electrically conductive pattern on a color reproduction receptor comprising a support and an image receptive lamina comprising a dark adaptable photoconductor which is photochemically stable at room temperature bonded to said support in the form of a plurality of three coplanar, laterally disposed, subtractively colored surface areas substantially coterminously adjacent one another, said subtractively colored surface areas being separately and visually colored cyan, magenta and yellow and said cyan, magenta and yellow colored surface areas being selectively sensitive to red, green and blue light, respectively, and treating the remaining colored areas with a solvent to mix the remaining colored areas.

References Cited by the Examiner UNITED STATES PATENTS 1,191,034 7/16 Rheinberg et al. 96-11 2,693,416 11/54 Butterfield 96-1 2,846,332 8/58 Nesty. 2,861,008 11/58 Hollman 117-34 2,875,054 2/59 Griggs et al. 2,890,174 6/59 Mayer 252-621 2,899,335 8/59 Straughan 117-37 2,912,343 11/59 Collins et al. 117-34 2,940,847 6/ 60 Kaprelian 92-1 2,959,481 11/60 Kucera. 2,962,374 11/ 60 Dessauer. 2,968,554 1/61 Land 96-290 2,975,147 3/61 Abbott et al. 260-292 2,993,787 7/61 Sugarman. 3,010,884 11/61 Johnson 96-1 3,041,169 6/62 Wielicki 96-1 3,057,788 10/62 Reithel 204-18 3,060,019 10/62 Johnson et al. 3,060,020 10/62 Greig. 3,078,231 2/ 63 Metcalfe 252-621 3,127,331 3/ 64 Neher 20'4-18 3,147,699 9/ 64 Land.

FOREIGN PATENTS 204,093 6/ 5 6 Australia.

222,523 1 0/ 24 Great Britain.

820,763 9/59 Great Britain.

888,371 "1/ 62 Great Britain. 1,249,167 11/ 60 France.

OTHER REFERENCES Floyd: Polyamide Resins, Reinhold, New York, 1958, pages 198-213.

Rydz et al.: RCA Review, September 1958, pages 465-483.

NORMAN G. TORCHIN, Primary Examiner.

HAROLD N. BURSTEIN, Examiner. 

10. A METHOD FOR MAKING A COLORED REPRODUCTION OF A COLORED IMAGE WHICH COMPRISES TO A COLORED LIGHT IMAGE OF COLOR REPRODUCTION RECEPTOR COMPRISING A SUPPORT AND AN IMAGE RECEPTIVE LAMINA COMPRISING A DARD ADAPTABLE INORGANIC PARTICULATE KPHOTOCONDUCTOR WHICH IS PHOTOCHEMICALLY STABLE AT ROOM TEMPERATURE BONDED TO SAID SUPPORT IN THE FORM OF A PLURALITY OF THREE COPLANAR, LATERALLY DISPOSED, SUBSTRACTIVELY COLORED SURFACE A AREAS SUBSTANTIALLY COTERMINOUSLY ADJACENT ONE ANOTHER; SAID SUBTRACTIVELY COLORED SURFACE AREAS BEING SEPARATELY AND VISUALLY COLORED CYANA, MAGENTA AND YELLOW WITH A CORRESPONDINGLY COLORED DYE AND SAID CYAN, MAGENTA AND YELLOW COLORED SURFACE AREAS BEING SELECTIVELY SENSITIVE TO RED, GREEN AND BLUE LIGHT, RESPECTIVELY, WITH A DIFFERENT CORRESPONDINGLY SENSITIVE DYE, TO FORM A DIFFERENTIALLY ELECTRICALLY CONDUCTIVE PATTERN CORRESPONDING TO SAID LIGHT IMAGE, ELECTROSTATICALLY DEPOSITING AN ELECTROSTATIC DEVELOPER POWDER COMPRISING A RESIN AND WHITE PIGMENT ON THE CONDUCTIVE AREAS OF SAID DIFIFERENTIALLY CONDUCTIVE PATTERN, AND FIXING SAID ELECTROSTATIC DEVELOPER POWDER ON SAID RECEPTOR. 